The prior art discloses a trolley having two upper supporting or traction wheels connected with a lower counterwheel by a parallelogram linkage. On a horizontal stretch of track, the counterwheel adheres to the rail without pressure, while on inclines it is pressed to the lower rail surfaces from below by the parallel displacement of the linkage. A disadvantage of this arrangement is that, should removal from and/or replacement upon the rail be necessary, this cannot be done without substantial disassembly of the entire mechanism.
It is the object of the present invention to provide a trolley truck structure which may easily be placed upon the rail and just as easily be removed therefrom. This is achieved, in accordance with the invention, by spacing the wheels (supporting or traction wheel, counterwheel which engage the upper and lower bearing surfaces of the rail) a greater distance apart than the actual vertical spacing between the two parallel bearing surfaces of the rail in a manner in which the center of gravity of both the loaded and empty trolley truck is laterally displaced with respect to the points of contact between the rail and the supporting wheel and the counterwheel, to cause both wheels to engage firmly and adhere to the rail. This design enhances the friction between rail and wheels which serves to secure the truck on the bearing surfaces of the rail, and, as in the case of certain modified embodiments, upon any guides arranged adjacent the rail or forming part of the rail. By having a greater distance between supporting and counterwheel than that between the bearing surfaces of the rail, it is possible to cancel the friction by pivoting the trolley truck, itself, about a horizontal lateral axis. In this position, the trolley may be easily removed from the rail by simultaneous tilting. If the traction wheel actually travels, as is also feasible in accordance with the principles of the invention, on a lower flight of the rail and the counter wheel adheres to an upper flight of the rail, the trolley is pivoted for removal from the rail in such a way that the wheels are positioned in approximately horizontal tandem fashion.
In accordance with the invention, no bolt connections or other mechanical assembly operations are required for installing and/or removing the trolley. In a preferred embodiment, the trolley is equipped with a single supporting or traction wheel and a single counterwheel. It may also be equipped with several supporting wheels arranged on a rocker arm, if desired in certain cases.
It has been found that a trolley truck constructed in accordance with this invention, may be guided perfectly along the rail during acceleration and deceleration, as well as when ascending or descending.
In order to establish the desired location of the center of gravity of the empty trolley, the motor driving the supporting wheel (the traction wheel) is located on the desired center of gravity side of the traction wheel, as will be understood.
The shaft of the supporting wheel and the axle of the counter wheel are arranged on a common trolley truck frame consisting of a central plate member on one side of the rail, the central plate being provided with an upper axle bearing journal box for the traction wheel and a lower axle bearing journal box for the counterwheel. The lower axle bearing journal box extends longitudinally of the trolley from the counter wheel support and intersects the vertical axis (vertical center line) of the supporting wheel. The trolley frame is equipped with a load suspension yoke which includes several bore holes for hooking up the load to the frame on a load axis displaced longitudinally from the vertical axis of the supporting wheel. If the trolley travels exclusively on a straight or downhill course, heavy loads are suspended from the bore hole nearest the vertical axis to avoid unduly excessive pressure moments. If, however, steep inclines have to be tranversed, or if the load is light, the bore hole farthest from the support wheel of the vertical axis is chosen for load suspension. This location is also laterally displaced with relation to the vertical axis of the counterwheel, due to the elevation of the counterwheel with respect to the supporting wheel on an inclined rail.
Furthermore, the trolley truck may be provided on both sides with horizontal guide wheels rotating about vertical axes and adhering to vertical bearing surfaces of the rail. When employing guide wheels, they are offset from the vertical axis, so that there are always front and rear guides for the trolley assuring proper operation.
The trolley frame is furthermore provided with an opening and a cover plate with attached current pick-ups, gliding along sliding lines which in turn are attached directly to the rail. The cover plate is, of course, somewhat larger than the frame opening and may be fastened to the frame with screws.
If the trolley is to ascend to 90.degree. incline, the supporting wheel is provided with a rim designed as a gear rim, and the rail on this uphill stretch, is provided with a rack-like surface for cooperation with the pinion teeth on the gear rim, in known fashion. The trolley may be equipped with an additional counterwheel, which is located on the side opposite the first counterwheel. The additional counterwheel is adapted to be easily removable so that the trolley may be tilted without any great effort.
In order to carry heavy loads, several trolleys may be connected via supporting rods, the latter being attached to the load suspension yoke.
For a better understanding of the present invention and a more complete appreciation of its attendant advantages, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.